UNITED NATIONS, Dec 31 (Reuters) - 'A U.N. Security Councilsanctions committee on Monday blacklisted two rebel groups thathave been responsible for war crimes in conflict-ravaged easternDemocratic Republic of the Congo, the United Nations said in astatement.

The United States and Britain praised the move, withWashington suggesting further sanctions may be imposed againstanyone who continues to cause trouble in eastern Congo.

One of the groups added to the blacklist is the so-calledM23, a Congolese rebel faction led by Bosco Ntaganda, a warlordindicted by the International Criminal Court.

M23 initially said they took up arms over what they calledKinshasa's failure to keep a 2009 peace deal that saw themintegrated into the army. They later broadened the scope oftheir movement, making its goal the "liberation" of all of Congoand the ouster of President Joseph Kabila.

The U.N. statement said M23, which is widely believed to bereceiving support from neighboring Rwanda, has been complicit inserious crimes such as "killing and maiming, sexual violence,abduction, and forced displacement."

No Rwandans have been sanctioned in connection with M23,which diplomats have said on condition of anonymity was becausethe United States, in particular, opposes any such moves ascounterproductive.

The other rebel organization hit with sanctions on Monday isthe FDLR, or Democratic Forces for the Liberation of Rwanda. TheFDLR is a Rwandan Hutu group that opposes President PaulKagame's Tutsi-led government in Kigali and includes Hutumilitiamen suspected of participating in Rwanda's 1994 genocide.

FDLR has been guilty of "targeting of women and children inarmed conflict in the DRC, including killing and maiming, sexualviolence, and forced displacement," the U.N. statement said.

RWANDA JOINS U.N. SECURITY COUNCIL

U.S. Ambassador to the United Nations Susan Rice welcomedthe Congo sanctions committee's decision.

"We urge the rank and file of both the M23 and the FDLR todefect and demobilize in order to disassociate themselves fromthe sanctioned groups," Rice said in a statement.

She said Washington and its partners "will continue to useevery tool at our disposal to maintain the pressure on thoseresponsible for the violence in the eastern DRC ... includingadditional action by the Security Council."

The committee's announcement came hours before Rwanda joinsthe 15-nation Security Council. Rwanda has vowed to help improvethe situation in eastern Congo during its upcoming stint on thecouncil, but says it will not tolerate continued attempts toblame it for the M23 insurgency.

Some council envoys told Reuters on condition of anonymitythat it may be more difficult to reach a consensus on issuesrelated to Congo with Rwanda on the council.

The Security Council's "Group of Experts" has accused Rwandaand Uganda of backing M23. Kigali and Kampala deny the group'sallegations but council diplomats say their denials are notcredible.

The council has previously sanctioned individual members ofM23 and FDLR, but not the groups themselves.

In addition to the two rebel groups, the sanctions committeeblacklisted two additional M23 leaders on Monday: Eric Badegeand Jean-Marie Runiga Lugerero. The two men will faceinternational travel bans and asset freezes.

The council's Group of Experts previously recommended thatthe sanctions committee blacklist Rwandan officials it says havebeen overseeing M23, including Rwandan Defense Minister JamesKabarebe, who the experts say is at the top of the M23 chain ofcommand. But the council has not acted on their recommendation.